Principles of epidemiological research on adverse and beneficial drug effects

Long-term ketamine infusion-induced cholestatic liver injury in COVID-19-associated acute respiratory distress syndrome

Background

A higher-than-usual resistance to standard sedation regimens in COVID-19 patients suffering from acute respiratory distress syndrome (ARDS) has led to the frequent use of the second-line anaesthetic agent ketamine. Simultaneously, an increased incidence of cholangiopathies in mechanically ventilated patients receiving prolonged infusion of high-dose ketamine has been noted. Therefore, the objective of this study was to investigate a potential dose–response relationship between ketamine and bilirubin levels.

Methods

Post hoc analysis of a prospective observational cohort of patients suffering from COVID-19-associated ARDS between March 2020 and August 2021. A time-varying, multivariable adjusted, cumulative weighted exposure mixed-effects model was employed to analyse the exposure–effect relationship between ketamine infusion and total bilirubin levels.

Results

Two-hundred forty-three critically ill patients were included into the analysis. Ketamine was infused to 170 (70%) patients at a rate of 1.4 [0.9–2.0] mg/kg/h for 9 [4–18] days. The mixed-effects model revealed a positively correlated infusion duration–effect as well as dose–effect relationship between ketamine infusion and rising bilirubin levels (p < 0.0001). In comparison, long-term infusion of propofol and sufentanil, even at high doses, was not associated with increasing bilirubin levels (p = 0.421, p = 0.258). Patients having received ketamine infusion had a multivariable adjusted competing risk hazard of developing a cholestatic liver injury during their ICU stay of 3.2 [95% confidence interval, 1.3–7.8] (p = 0.01).

Conclusions

A causally plausible, dose–effect relationship between long-term infusion of ketamine and rising total bilirubin levels, as well as an augmented, ketamine-associated, hazard of cholestatic liver injury in critically ill COVID-19 patients could be shown. High-dose ketamine should be refrained from whenever possible for the long-term analgosedation of mechanically ventilated COVID-19 patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-022-04019-8.

Modeling of cumulative effects of time-varying drug exposures on within-subject changes in a continuous outcome

An accurate assessment of the safety or effectiveness of drugs in pharmaco-epidemiological studies requires defining an etiologically correct time-varying exposure model, which specifies how previous drug use affects the outcome of interest. To address this issue, we develop, and validate in simulations, a new approach for flexible modeling of the cumulative effects of time-varying exposures on repeated measures of a continuous response variable, such as a quantitative surrogate outcome, or a biomarker. Specifically, we extend the linear mixed effects modeling to estimate how past and recent drug exposure affects the way individual values of the outcome change throughout the follow-up. To account for the dosage, duration and timing of past exposures, we rely on a flexible weighted cumulative exposure methodology to model the cumulative effects of past drug use, as the weighted sum of past doses. Weights, modeled with unpenalized cubic regression B-splines, reflect the relative importance of doses taken at different times in the past. In simulations, we evaluate the performance of the model under different assumptions concerning (i) the shape of the weight function, (ii) the sample size, (iii) the number of the longitudinal observations and (iv) the intra-individual variance. Results demonstrate the accuracy of our estimates of the weight function and of the between- and within-patients variances, and good correlation between the observed and predicted longitudinal changes in the outcome. We then apply the proposed method to re-assess the association between time-varying glucocorticoid exposure and weight gain in people living with rheumatoid arthritis.

Aspirin and Risk of Gastric Cancer After Helicobacter pylori Eradication: A Territory-Wide Study

Background

Despite successful H. pylori (HP) eradication, some individuals remain at risk of developing gastric cancer (GC). Previous studies showed that aspirin was associated with a reduced GC risk. However, whether aspirin can reduce GC risk in HP-eradicated subjects remains unknown. We aimed to determine the chemopreventive effect of aspirin in HP-eradicated subjects.

Methods

We identified subjects who had received a prescription of clarithromycin-based triple therapy for HP between 2003 and 2012 from a territory-wide health care database. The observation period started from commencement of HP therapy (index date), and the follow-up was censored at the end of the study (December 2015), death, or GC diagnosis. Aspirin use was defined as use once or more often weekly. Subjects who failed HP eradication or were diagnosed with GC within 12 months of HP therapy were excluded. The hazard ratio (HR) of GC with aspirin use was calculated by Cox model with Propensity Score adjustment for age, sex, comorbidities, and concurrent medications. All statistical tests were two-sided.

Results

The median follow-up was 7.6 years (interquartile range [IQR] = 5.1-10.3 years), and 169 (0.27%) out of 63 605 patients developed GC. The incidence rate of GC was 3.5 per 10 000 person-years. Aspirin use was associated with a reduced GC risk (HR = 0.30, 95% confidence interval [CI] = 0.15 to 0.61). The risk of GC decreased with increasing frequency, duration, and dose of aspirin (all Ptrend < .001).

Conclusions

Aspirin use was associated with a frequency-, dose-, and duration-dependent reduction in GC risk after HP eradication. The effect was most prominent in those who used aspirin daily or for five or more years.

Competing risks modeling of cumulative effects of time-varying drug exposures

An accurate assessment of drug safety or effectiveness in pharmaco-epidemiology requires defining an etiologically correct time-varying exposure model, which specifies how previous drug use affects the hazard of the event of interest. An additional challenge is to account for the multitude of mutually exclusive events that may be associated with the use of a given drug. To simultaneously address both challenges, we develop, and validate in simulations, a new approach that combines flexible modeling of the cumulative effects of time-varying exposures with competing risks methodology to separate the effects of the same drug exposure on different outcomes. To account for the dosage, duration and timing of past exposures, we rely on a spline-based weighted cumulative exposure modeling. We also propose likelihood ratio tests to test if the cumulative effects of past exposure on the hazards of the competing events are the same or different. Simulation results indicate that the estimated event-specific weight functions are reasonably accurate, and that the proposed tests have acceptable type I error rate and power. In real-life application, the proposed method indicated that recent use of antihypertensive drugs may reduce the risk of stroke but has no effect on the hazard of coronary heart disease events.

The Individual Perspective: Did This Vaccine Harm this Person?

With the rapid pace of immunologic research, it is more important than ever for readers to understand rational immunodiagnosis, immunoprophylaxis, and immunotherapy. This column is intended to help you carry out proper immuno-logic drug use in your practice.

Association of thiazolidinediones with gastric cancer in type 2 diabetes mellitus: a population-based case-control study

BACKGROUND

It has been shown that peroxisome proliferator-activated receptors (PPAR) have physiological and pharmacological ligands. The objective is to assess the association between thiazolidinediones (TZDs) and the occurrence of gastric cancer.

METHODS

We conducted a population-based nested case-control study. Data were retrospectively collected from the National Health Insurance Research Database (NHIRD). The cases consisted of all diabetes mellitus (DM) patients aged 30 to 99 years, and who had a first time diagnosis of gastric cancer in the study cohort. The controls were matched to cases by age, sex, and index date. The adjusted odds ratio (OR) and 95% confidence interval (CI) were estimated by using multiple logistic regression.

RESULTS

Records from 357 gastric cancer and 1,428 selected matched controls were included in the analyses of gastric cancer risk. A total of 7% or 9.5% of the cases and 10.8% or 14.8% of the controls had used any quantity of at least 2 prescriptions for pioglitazone or rosiglitazone, respectively. After adjusting for possible confounders, pioglitazone (OR = 0.93, P > 0.05) and rosiglitazone (OR = 1.21, P > 0.05), had no significant association of decreasing gastric cancer. After adjusting for possible confounders, pioglitazone (OR = 0.70, P > 0.05) or rosiglitazone (OR = 0.79, P > 0.05), had no significant trend toward decreasing gastric cancer risk with increasing cumulative doses ≥ 260 defined daily doses (DDDs), respectively. Moreover, adjusting for possible confounders pioglitazone (OR = 0.68, P > 0.05) or rosiglitazone (OR = 0.74, P > 0.05) had no significant trend toward decreasing gastric cancer risk with increasing cumulative doses ≥ 1 year, respectively.

CONCLUSIONS

Our results did not show evidence to support that TZD derivatives in DM patients reduces gastric cancer occurrence.

Association of thiazolidinediones with liver cancer and colorectal cancer in type 2 diabetes mellitus

The objective of this nationwide case-control study was to evaluate the risk of specific malignancy in diabetic patients who received thiazolidinediones (TZDs). A total of 606,583 type 2 diabetic patients, age 30 years and above, without a history of cancer were identified from the Taiwan National Health Insurance claims database during the period between January 1 2000 and December 31 2000. As of December 31 2007, patients with incident cancer of liver, colorectal, lung, and urinary bladder were included as cases and up to four age- and sex-matched controls were selected by risk-set sampling. Logistic regression models were applied to estimate the odds ratio (OR) and 95% confidence interval (CI) between TZDs and cancer incidence. A total of 10,741 liver cancer cases, 7,200 colorectal cancer cases, and 70,559 diabetic controls were included. A significantly lower risk of liver cancer incidence was found for any use of rosiglitazone (OR: 0.73, 95% CI: 0.65-0.81) or pioglitazone (OR: 0.83, 95% CI: 0.72-0.95), respectively. The protective effects were stronger for higher cumulative dosage and longer duration. For colorectal cancer, rosiglitazone, but not pioglitazone, was associated with a significantly reduced risk (OR: 0.86; 95% CI: 0.76-0.96). TZDs were not associated with lung and bladder cancer incidence, although a potential increased risk for bladder cancer with pioglitazone use ≥3 years could not be excluded (OR: 1.56; 95% CI: 0.51-4.74).

CONCLUSION

The use of pioglitazone and rosiglitazone is associated with a decreased liver cancer incidence in diabetic patients. The effects on occurrence of specific cancer types may be different for pioglitazone and rosiglitazone.

Meta-analyses of adverse effects data derived from randomised controlled trials as compared to observational studies: methodological overview

BACKGROUND

There is considerable debate as to the relative merits of using randomised controlled trial (RCT) data as opposed to observational data in systematic reviews of adverse effects. This meta-analysis of meta-analyses aimed to assess the level of agreement or disagreement in the estimates of harm derived from meta-analysis of RCTs as compared to meta-analysis of observational studies.

METHODS AND FINDINGS

Searches were carried out in ten databases in addition to reference checking, contacting experts, citation searches, and hand-searching key journals, conference proceedings, and Web sites. Studies were included where a pooled relative measure of an adverse effect (odds ratio or risk ratio) from RCTs could be directly compared, using the ratio of odds ratios, with the pooled estimate for the same adverse effect arising from observational studies. Nineteen studies, yielding 58 meta-analyses, were identified for inclusion. The pooled ratio of odds ratios of RCTs compared to observational studies was estimated to be 1.03 (95% confidence interval 0.93-1.15). There was less discrepancy with larger studies. The symmetric funnel plot suggests that there is no consistent difference between risk estimates from meta-analysis of RCT data and those from meta-analysis of observational studies. In almost all instances, the estimates of harm from meta-analyses of the different study designs had 95% confidence intervals that overlapped (54/58, 93%). In terms of statistical significance, in nearly two-thirds (37/58, 64%), the results agreed (both studies showing a significant increase or significant decrease or both showing no significant difference). In only one meta-analysis about one adverse effect was there opposing statistical significance.

CONCLUSIONS

Empirical evidence from this overview indicates that there is no difference on average in the risk estimate of adverse effects of an intervention derived from meta-analyses of RCTs and meta-analyses of observational studies. This suggests that systematic reviews of adverse effects should not be restricted to specific study types. Please see later in the article for the Editors' Summary.

Risk of venous thromboembolism in users of oral contraceptives containing drospirenone or levonorgestrel: nested case-control study based on UK General Practice Research Database

OBJECTIVE

To examine the risk of non-fatal idiopathic venous thromboembolism in current users of a combined oral contraceptive containing drospirenone, relative to current users of preparations containing levonorgestrel.

DESIGN

Nested case-control study.

SETTING

UK General Practice Research Database.

PARTICIPANTS

Women aged 15-44 years without major risk factors for venous thromboembolism who started a new episode of use of an oral contraceptive containing 30 µg oestrogen in combination with either drospirenone or levonorgestrel between May 2002 and September 2009. Cases were women with a first diagnosis of venous thromboembolism; up to four controls, matched by age, duration of recorded information, and general practice, were randomly selected for each case.

MAIN OUTCOME MEASURES

Odds ratios and 95% confidence intervals estimated with conditional logistic regression; age adjusted incidence rate ratio estimated with Poisson regression.

RESULTS

61 cases of idiopathic venous thromboembolism and 215 matched controls were identified. In the case-control analysis, current use of the drospirenone contraceptive was associated with a threefold higher risk of non-fatal idiopathic venous thromboembolism compared with levonorgestrel use; the odds ratio adjusted for body mass index was 3.3 (95% confidence interval 1.4 to 7.6). Subanalyses suggested that referral, diagnostic, first time user, duration of use, and switching biases were unlikely explanations for this finding. The crude incidence rate was 23.0 (95% confidence interval 13.4 to 36.9) per 100,000 woman years in current users of drospirenone and 9.1 (6.6 to 12.2) per 100,000 woman years in current users of levonorgestrel oral contraceptives. The age adjusted incidence rate ratio was 2.7 (1.5 to 4.7).

CONCLUSIONS

These findings contribute to emerging evidence that the combined oral contraceptive containing drospirenone carries a higher risk of venous thromboembolism than do formulations containing levonorgestrel.

Proton pump inhibitor use and risk of hip fractures in patients without major risk factors

STUDY OBJECTIVE

To estimate the relative risk of hip fracture associated with proton pump inhibitor (PPI) use in a population without major risk factors.

DESIGN

A two-phase, matched, nested case-control study.

DATA SOURCE

United Kingdom General Practice Research Database (GPRD).

PATIENTS

Phase 1 identified 4414 case patients (aged 50-79 yrs) with an incident hip fracture between 1995 and 2005 who had at least 2 years of recorded history in the GPRD; each case was matched by age, sex, and index date (date of first-time hip fracture for cases, same date for matched controls) to up to 10 controls who did not have hip fracture. Phase 2 included the 1098 case patients identified as having no major medical risk factors for hip fracture (as assessed in phase 1) and a new set of 10,923 controls without major risk factors for hip fracture matched by sex, age, index date, and duration of history in the GPRD.

MEASUREMENTS AND MAIN RESULTS

In phase 1, we identified major medical risk factors for hip fracture. In phase 2, we restricted the study to case patients with none of these risk factors and matched them to new controls, who also had none of the risk factors. Data on use of PPIs were collected and compared between the groups. The relative risk (RR) for hip fracture among patients who received any PPI prescription was 0.9 (95% confidence interval 0.7-1.1) compared with those with no PPI prescription. We found no evidence of an increased risk of hip fracture with increased PPI use. The RR estimates were similar in both sexes and in all age subgroups. No specific PPI was associated with an increased risk of hip fracture.

CONCLUSION

Use of PPIs does not increase the risk of hip fracture in patients without major risk factors. The difference in results between our study and that of another, which indicated that PPI use increases the risk of hip fracture, may be due to residual confounding or effect modification in the latter study.

Nonsteroidal antiinflammatory drugs and acute myocardial infarction in patients with no major risk factors

STUDY OBJECTIVE

To assess the risk of long-term use of five nonsteroidal antiinflammatory drugs (NSAIDs)--rofecoxib, celecoxib, ibuprofen, naproxen, and diclofenac--in relation to acute myocardial infarction.

DESIGN

Five separate nested case-control studies, one for each NSAID, designed to minimize important biases present in other observational studies. Setting. University-affiliated research program. Data Source. The United Kingdom General Practice Research Database (GPRD).

MEASUREMENTS AND MAIN RESULTS

We identified all people in the GPRD aged 30-79 years who had a first recorded prescription for rofecoxib, celecoxib, ibuprofen, naproxen, or diclofenac after January 1, 1999. Cases of newly diagnosed, first-time acute myocardial infarction were then identified from the study population, along with matched control subjects. Relative risk estimates for acute myocardial infarction in patients with no recorded major clinical risk factors for acute myocardial infarction were determined for each NSAID according to receipt of 2-4, 5-9, 10-19, or 20 or more prescriptions compared with receipt of only 1 prescription. Results were adjusted for relevant variables possibly related to the risk for acute myocardial infarction. No material elevation of risk according to the number of prescriptions received for ibuprofen or naproxen was noted. However, a substantial increased risk similar to that found in clinical trials was noted in patients who received 10 or more prescriptions for rofecoxib, celecoxib, or diclofenac.

CONCLUSION

Extensive use of rofecoxib, celecoxib, and diclofenac increases the risk of acute myocardial infarction, but similar use of ibuprofen and naproxen does not.

Assessing the impact of prescribed medicines on health outcomes

This paper reviews methods that can be used to assess the impact of medicine use on population health outcomes. In the absence of a gold standard, we argue that a convergence of evidence from different types of studies using multiple methods of independent imperfection provides the best bases for attributing improvements in health outcomes to the use of medicines. The major requirements are: good evidence that a safe and effective medicine is being appropriately prescribed; covariation between medicine use and improved health outcomes; and being able to discount alternative explanations of the covariation (via covariate adjustment, propensity analyses and sensitivity analyses), so that medicine use is the most plausible explanation of the improved health outcomes. The strongest possible evidence would be provided by the coherence of the following types of evidence: (1) individual linked data showing that patients are prescribed the medicine, there are reasonable levels of patient compliance, and there is a relationship between medicine use and health improvements that is not explained by other factors; (2) ecological evidence of improvements in these health outcomes in the population in which the medicine is used. Confidence in these inferences would be increased by: the replication of these results in comparable countries and consistent trends in population vital statistics in countries that have introduced the medicine; and epidemiological modelling indicating that changes observed in population health outcomes are plausible given the epidemiology of the condition being treated.

Risk of acute myocardial infarction with nonselective non-steroidal anti-inflammatory drugs: a meta-analysis

The use of cyclo-oxygenase 2 selective nonsteroidal anti-inflammatory drugs (NSAIDs) is associated with increased risk of acute myocardial infarction (AMI). The association between the risks of AMI with nonselective NSAIDs is less clear. We reviewed the published evidence and assessed the risk of AMI with nonselective NSAIDs. We performed a meta-analysis of all studies containing data from population databases that compared the risk of AMI in NSAID users with that in non-users or remote NSAID users. The primary outcome was objectively confirmed AMI. Fourteen studies met predefined criteria for inclusion in the meta-analysis. Nonselective NSAIDs as a class was associated with increased AMI risk (relative AMI risk 1.19, 95% confidence interval [CI] 1.08 to 1.31). Similar findings were found with diclofenac (relative AMI risk 1.38, 95% CI 1.22-1.57) and ibuprofen (relative AMI risk 1.11, 95% CI 1.06 to 1.17). However, this effect was not observed with naproxen (relative AMI risk 0.99, 95% CI 0.88-1.11). In conclusion, based on current evidence, there is a general direction of effect, which suggests that at least some nonselective NSAIDs increase AMI risk. Analysis based on the limited data available for individual NSAIDs, including diclofenac and ibuprofen, supported this finding; however, this was not the case for naproxen. Nonselective NSAIDs are frequently prescribed, and so further investigation into the risk of AMI is warranted because the potential for harm can be substantial.

Postmenopausal hormone replacement therapy and risk of acute pancreatitis: a population-based case-control study

OBJECTIVES

To examine whether acute pancreatitis is associated with the use of postmenopausal hormonal replacement therapy in Danish women over 45 yr of age.

METHODS

We based this population-based case-control study on data from three Danish counties for the years 1991-2003. We identified all women (>45 yr of age) with a first hospital discharge diagnosis of acute pancreatitis in the county hospital discharge registries (N = 1,054). Using the Danish Civil Registration System, we selected 10 age-matched population controls for each case, using risk set sampling (N = 10,540). Data on all prescriptions for estrogens or combined estrogen/progestins redeemed within 90 days before the hospitalization (current users) and 91-365 days before (former users) were collected from the prescription databases. Conditional logistic regression was used to estimate the relative risk of acute pancreatitis after exposure to estrogen or combined estrogen/progestin, adjusted for other risk factors for acute pancreatitis.

RESULTS

The adjusted relative risk for acute pancreatitis in current users of menopausal estrogens was 1.1 (95% confidence interval [CI] 0.8-1.4), and 1.1 (95% CI 0.8-1.5) in former users. For current users of combined estrogen/progestins, the adjusted relative risk was 1.2 (95% CI 0.9-1.6), and for former users, 1.6 (95% CI 1.0-2.5).

CONCLUSIONS

Our data did not support a substantial association between acute pancreatitis and the use of postmenopausal hormone therapy.

Generating psychotropic drug exposure data from computer-based medical records

PURPOSE

To develop a methodology for extracting psychotropic drug exposure data from computer-based medical records and for generating drug exposure variables suitable for secondary use.

METHODS

In South-Verona, Italy, a registry including every patient receiving psychotropic medications is operating since 2004. The basic structure of the registry is the medication record. Each record stores data on a specific prescription, and patients with more than one prescription have more than one record.

RESULTS

The longitudinal history of drug use was described identifying consecutive prescriptions of a specific drug, concomitant prescriptions of a specific drug and distinct prescriptions of a specific drug. Consecutive prescriptions implies that the beginning of the second prescription coincides with the end of the first prescription, concomitant prescriptions implies that the beginning of the second prescription precedes the end of the first prescription, distinct prescriptions implies that a gap of at least 1 day exists between prescriptions. Using this framework of drug representation, we identified episodes of drug therapy, where each episode is constituted of consecutive and/or concomitant prescriptions. Within each episode, prescriptions were categorised into theoretical phases, where the beginning of the new phase always coincides with the end of the previous phase. On the basis of this data representation, a module operating in Access and using Visual Basic for Applications was developed for creating episodes and phases on a routine basis (available from authors). A graphical representation of this conceptual model is presented.

CONCLUSION

The development of a simple methodology for extracting and generating drug exposure data suitable for secondary use will allow a better understanding of the beneficial and adverse consequences of psychotropic drug use in ordinary practice.

Antipsychotic drugs and diabetes--an application of the Austin Bradford Hill criteria

There is concern that antipsychotic drugs cause diabetes. Although there has been an explosion in the quantity of literature about this subject, it remains confusing and inconsistent. To assess whether the association between antipsychotic drugs and diabetes is causative, we applied the Austin Bradford Hill criteria to the available evidence. In support of a causative relationship, there is temporality for some cases of diabetes, and there is a biologically plausible explanation. The causative link between antipsychotic drugs and diabetes is coherent with our understanding of diabetes and there are other analogies. However the strength of association is weak, there is lack of consistency or specificity, and there is little evidence to support a biological gradient. We should therefore conclude that the evidence surrounding a causative link between antipsychotic drugs and diabetes is inconclusive. Moreover, the risk is probably low and the attributable risk of developing diabetes is greater for traditional risk factors such as family history, ethnicity, obesity and ageing than it is for receiving an antipsychotic drug. Consequently, the majority of patients receiving second-generation antipsychotics will not develop diabetes as a result of their medication.

An analysis of the exclusion criteria used in observational pharmacoepidemiological studies

PURPOSE

The application of exclusion criteria in pharmacoepidemiological studies could have a major impact on the findings but there appears to have been no previous research to examine the types of exclusion criteria applied.

METHODS

We searched the literature and identified 10 senior pharmacoepidemiologists who had published five or more relevant papers between 1999 and 2004. All their published drug safety studies during this period were reviewed. A classification system was developed to categorise the exclusion criteria, with 5 categories and 11 sub-categories. The categories were: (1) data quality and validation, (2) disease-related, (3) exposure-related, (4) patient characteristics and (5) miscellaneous reasons. Within each sub-category, only the first exclusion criterion identified for that study was counted.

RESULTS

We identified 200 studies, from which a total of 752 exclusion criteria sub-categories had been applied (mean 3.8 per study; between-author range of means 2.8-5.1). At the category level, exclusion criteria relating to data quality and validation were the most commonly applied (87% of publications), followed by patient characteristics (75%), disease-related (69%), exposure-related (38%) and miscellaneous (3%). The main categories for which research practice appeared to differ were those relating to diseases and exposures. The application of sub-category 'risk factors and alternative causes' varied between authors from 0% to 81% of studies, and for the sub-category 'medication of interest' it varied from 5% to 93%.

CONCLUSIONS

There are important differences between investigators in the application of exclusion criteria in pharmacoepidemiological studies. It is likely that a substantial part of the observed variation reflects different research practices of investigators.

Modeling cumulative dose and exposure duration provided insights regarding the associations between benzodiazepines and injuries

BACKGROUND AND OBJECTIVES

Accurate assessment of medication impact requires modeling cumulative effects of exposure duration and dose; however, postmarketing studies usually represent medication exposure by baseline or current use only. We propose new methods for modeling various aspects of medication use history and employment of them to assess the adverse effects of selected benzodiazepines.

STUDY DESIGN AND SETTING

Time-dependent measures of cumulative dose or duration of use, with weighting of past exposures by recency, were proposed. These measures were then included in alternative versions of the multivariable Cox model to analyze the risk of fall related injuries among the elderly new users of three benzodiazepines (nitrazepam, temazepam, and flurazepam) in Quebec. Akaike's information criterion (AIC) was used to select the most predictive model for a given benzodiazepine.

RESULTS

The best-fitting model included a combination of cumulative duration and current dose for temazepam, and cumulative dose for flurazepam and nitrazepam, with different weighting functions. The window of clinically relevant exposure was shorter for flurazepam than for the two other products.

CONCLUSION

Careful modeling of the medication exposure history may enhance our understanding of the mechanisms underlying their adverse effects.

Risk of nonfatal venous thromboembolism in women using a contraceptive transdermal patch and oral contraceptives containing norgestimate and 35 microg of ethinyl estradiol

CONTEXT

There is concern that a new transdermal contraceptive patch containing ethinyl estradiol (EE) and the progestin norelgestromin increases the risk for venous thromboembolism (VTE) compared to previously marketed oral contraceptives (OCs).

OBJECTIVE

Quantitative information was obtained on the risk of nonfatal VTE in women using the contraceptive patch in comparison to women using OCs, norgestimate (either monophasic or triphasic) and 35 microg EE (norgestimate-35), an OC that has been marketed for over a decade.

DESIGN, SETTING AND PARTICIPANTS

Nested case-control design based on information from PharMetrics, a US-based company that collects and organizes information on claims paid by managed care plans. The study was nested among all women aged 15 to 44, who started either the contraceptive patch or norgestimate-35 after April 1, 2002. Cases were women with current use of one of these two study drugs and a documented diagnosis of VTE in the absence of identifiable clinical risk factors (idiopathic VTE). Up to four controls were matched to each case by age and calendar time.

MAIN OUTCOME MEASURES

Odds ratios (ORs) comparing the risk of nonfatal VTE in new users of the two contraceptives and incidence rates of nonfatal VTE for new users of each of the study contraceptives.

RESULTS

We identified 68 newly diagnosed, idiopathic cases of VTE in the study population. In the case-control analysis, the OR comparing the contraceptive patch to norgestimate-35 was 0.9 (95% CI 0.5-1.6). The overall incidence rate for VTE was 52.8 per 100,000 women-years (95% CI 35.8-74.9) among users of the contraceptive patch and 41.8 per 100,000 women-years among users of norgestimate-35 (95% CI 29.4-57.6), and the age-adjusted VTE incidence rate ratio (IRR) for current use of the contraceptive patch vs. norgestimate-35 was 1.1 (95% CI 0.7-1.8).

CONCLUSIONS

The risk of nonfatal VTE for the contraceptive patch is similar to the risk for OCs containing 35 microg ethinylestradiol and norgestimate.

Pharmacovigilance during the Pre-Approval Phases

Pharmacovigilance science has traditionally been a discipline focussed on the postmarketing or post-authorisation period, with due attention directed towards pre-clinical safety data, clinical trials and adverse events. As the biological sciences have evolved, pharmacovigilance has slowly shifted toward earlier, proactive consideration of risks and potential benefits of drugs in the pre- and peri-approval stages of drug development, leading to a maturing of drug safety risk management. Further advances in biology, pharmacology and improvements in computational applications to medicine have led to the development of more complex medicines previously unobtainable and have also permitted a more thorough assessment of risks and potential benefits even earlier in the development process. Elevated public concern with the safety of more sophisticated medicines, combined with new science, have led pharmaceutical innovators, regulators and healthcare professionals to collaborate to develop guidelines, which drive enhanced pharmacovigilance and safety risk management earlier in drug development. In this paper, we review international guidelines on pharmacovigilance planning applicable to the pre-approval phases of medicines development and provide author opinion on these guidelines' potential drug safety implications. We discuss the possible evolution of a pharmaceutical industry model to respond to these guidelines; a view on multidisciplinary safety management teams is provided to encourage refinement of safety-signal identification and risk assessment early in drug development and to communicate important safety concerns to internal research efforts, patients, investigators and regulators. We further describe these functions in the context of the complexities of vulnerable populations, including the example of medicines research for paediatric populations. We also discuss the special role of epidemiology in pre-approval drug development and the impact on epidemiological science of changes to the pharmacovigilance paradigm.

Comparaison des prescriptions des pédiatres et des médecins généralistes : une étude en population en Franche-Comté sur la base de données de la caisse régionale d'assurance maladie

OBJECTIVES

To compare the medical management of children by private pediatricians or by general practitioners.

POPULATION AND METHODS

A retrospective cohort study analyzed information from the automated database of the Regional Health Insurance Fund for salaried workers in Franche-Comté from January 2001 through December 2002 and compared the mean rates of prescriptions in the populations seen only by general practitioners or mainly by pediatricians.

RESULTS

Analysis concerned 1 535 208 visits (office and home). Management by pediatricians was associated with 25% fewer consultations and 6% fewer hospitalizations. Pediatricians also wrote 25% fewer prescriptions for drugs, 17% fewer for laboratory tests, and 42% fewer for speech and language therapy. Children seen by pediatricians took antibiotics much less often (penicillin: -24%; cephalosporins: -74%; macrolides: -53%) as well as half as many corticoids and NSAIDs. Their vaccination coverage was more complete (31% more hepatitis B vaccines, 7% more MMR), as was prevention against rickets and cavities (twice the rate of vitamin D and fluoride prescriptions). The population followed mainly by pediatricians included 25% more children with a chronic disease.

CONCLUSION

General practitioners and pediatricians appear to differ significantly in their management of children. Other studies that can take into account such confounding factors as health status are needed to confirm these results.

Development of a registry for monitoring psychotropic drug prescriptions: aims, methods and implications for ordinary practice and research

In psychiatry, individual-based registries have provided key information on risks and benefits associated with the use of psychotropic drugs but they have rarely been employed for monitoring and evaluating the everyday prescribing of psychopharmacological treatments. This article describes the cultural background that gave impetus to the idea of registering all prescriptions of psychotropic drugs dispensed by physicians working in the South Verona community mental health service, and presents the methodology employed to develop such a registry in a community psychiatric service where a psychiatric case register (PCR) has been operating since 1978. We developed a registry including every patient receiving psychotropic medications in ordinary practice. This registry is linked to the PCR in order to obtain data on social and demographic characteristics, clinical symptoms, diagnosis, use of services, and outcomes. No exclusion criteria are allowed--anyone receiving treatment is automatically included. This system, which can link drug and service-use data with hard outcome indicators, can generate information on the proportion of subjects discontinuing treatment, switching medication because of side-effects, recovery or inefficacy, as well as on the proportion of subjects failing to return to the physician, and the proportion of patients who improve. The innovative aspect of this approach is that this registry is developed, organized and used by physicians interested in monitoring their clinical practice and in providing patients, relatives and the public with accurate information on drug use in their specific context of care.

Guidelines for prescribing azathioprine in dermatology

Azathioprine has been available as an immunosuppressive agent for over 40 years, and current routine usage in dermatology is not restricted to licensed indications. Advances in understanding the metabolic fate of azathioprine have led to significant changes in prescribing practice and toxicity monitoring by U.K. dermatologists. The current state of knowledge concerning the use of azathioprine in dermatology is summarized, with identification of strength of evidence. Clinical indications and contraindications for azathioprine usage in dermatology are identified. Evidence-based recommendations are made for routine safety monitoring of patients treated with azathioprine, including pretreatment assessment of red blood cell thiopurine methyltransferase activity.

Pharmacoepidemiology II: The Nested Case-Control Study–A Novel Approach in Pharmacoepidemiologic Research

This article on pharmacoepidemiology, the second of two parts, is a more focused discussion of the methodology of cohort studies and case-control studies, the basic methodologies of which were discussed in part I. The nested case-control study incorporates the strengths of both the cohort and case-control studies but may alleviate some of the methodologic challenges inherent in both types of studies. In a nested case-control study, a cohort of individuals is followed during certain time periods until a certain outcome is reached. The analysis is conducted as a case-control study in which cases are matched to only a sample of control subjects. Matching allows for control of potential confounding variables such as age, calendar time, and disease duration. Also, the time dependency of an exposure can be quantified without complicated statistical techniques. Matching the cases and controls by time allows the investigator to stratify exposure based on current, past, or intermittent use. By using the principles of epidemiology, the nested case-control study allows for the control of confounding variables, as well as better quantification of time-dependent exposures.

A design for prescription-event monitoring in Japan (J-PEM)

OBJECTIVES

To present a design for Prescription-Event Monitoring in Japan (J-PEM).

METHODS

In J-PEM, pharmacists are asked to register patients who are prescribed the 'test drug' or a 'control drug' for the first time ever, the drug, and prescribing physician. Although J-PEM does not identify all users of a drug, this method provides concurrent controls. In J-PEM, a questionnaire for the pharmacist and one for the prescribing physician are mailed 6 months after the drug to be monitored is first prescribed to a patient. Doctors and pharmacists are asked to report events that occurred in the patient after the drug was prescribed. The questionnaire for the physician includes questions that are specific to the class of drug that was prescribed, to obtain information on possible confounding variables. Pharmacists are requested to give information on all concomitant drugs used by the patient during or for a part of the period that the patient was taking the drug to be monitored.

RESULTS AND CONCLUSIONS

Compared with the UK PEM, the weakness of J-PEM is its inability to identify all users of a drug, and its strengths are the availability of concurrent controls and a relatively large amount of information per patient.

Generating signals of drug-adverse effects from prescription databases and application to the risk of arrhythmia associated with antibacterials

BACKGROUND

Although it is well known that a variety of antibacterials may incidentally cause malignant arrhythmia, the list of drugs causing arrhythmia and the impact of these adverse effects are still uncertain. We investigated on this topic by using a large prescription database with different observational designs.

METHODS

Prescription data on all incident users of several antibacterial and antiarrhythmic drugs over the period July 1997 through December 1999 were retrieved from the Drug Prescription Database (DPD) of the Italian Province of Varese. The association between the use of antibacterial and antiarrhythmic drugs was investigated by applying prescription sequence symmetry, cohort and nested case-control designs.

RESULTS

Lower proarrhythmic effects were on an average obtained from prescription sequence symmetry approach with respect to both cohort and nested case-control. Evidence of association between exposure to drugs (erythromycin and ciprofloxacin) and the risk of arrhythmia was consistently found by the three approaches. No other signals were generated from the prescription sequence symmetry analysis. Two drugs (clarithromycin and levofloxacin) showed patterns compatible with an arrhythmic effect according to both cohort and nested case-control designs.

CONCLUSIONS

Prescription databases are useful tools to explore drug safety through both conventional and emerging observational designs. In spite of its appealing features, prescription sequence symmetry design shows lower sensitivity with respect to conventional designs. Evidence about the association between the use of certain macrolides and fluoroquinolones and the onset of arrhythmia is confirmed by this study.

Approaches to combat with confounding by indication in observational studies of intended drug effects

There has been a resurgence of controversy about the usefulness of observational data to study the efficacy of drugs. Nearly every week a researcher makes some criticism of clinical trials or justifies observational research into intended effects, with other researchers offering a contradictory viewpoint. Literature reviews are not useful in this regard because the contradictory studies will not usually be carried out. Some methods are discussed which may have potential utility in the study of intended effects. There may be a marginal role for statistical techniques such as propensity scores and confounder scores. More promising techniques may include ecological analyses, restriction of subjects and blinded prospective review. Because it is currently unknown when the observational study of drug efficacy is possible, we should arguably always carry out a study of the determinants of prescribing first, and possibly consider using the various techniques that are outlined in this article.

The epidemiology of fragrance allergy: questions and needs

BACKGROUND

There are still open questions about the safety of fragrances.

OBJECTIVES

To evaluate the evidence concerning the frequency of contact dermatitis to fragrances in the general population and selected subgroups and the risk factors for sensitization and clinical manifestations.

METHODS

Review of published data.

RESULTS

No criteria for a reliable diagnosis of 'contact dermatitis' are available. International recommendations and standardization for patch test methods exist; however, the question whether agents that are positive are causally linked to contact dermatitis remain fraught with uncertainties concerning false-positive rates and clinical relevance. Most of the discussion concerning prevalence or incidence variations of allergic contact dermatitis to fragrances concentrate on the frequency of positive patch tests in clinical series, i.e. 'floating numerators'.

CONCLUSIONS

Risk assessment requires that data from different sources are integrated and compared. Both a 'sentinel surveillance' system and more refined epidemiological studies in well-defined populations are needed to reliably assess the risks associated with fragrance exposure.

Use of nonsteroidal anti-inflammatory drugs and the risk of first-time acute myocardial infarction

AIMS

Aspirin decreases the risk of clinical manifestations of atherothrombosis. This effect is mainly due to inhibition of platelet aggregation and potentially due to anti-inflammatory properties of aspirin. To evaluate whether use of non-aspirin non-steroidal anti-inflammatory drugs (NSAIDs) may also be associated with a decreased risk of first-time acute myocardial infarction (AMI), we performed a population-based case-control analysis using the United Kingdom-based General Practice Research Database (GPRD) METHODS: We identified first-time AMI-patients free of preexisting diagnosed cardiovascular or metabolic diseases. We compared use of NSAIDs prior to the index date between cases and control patients who were matched to cases on age, gender, practice and calendar time.

RESULTS

A total of 3319 cases (<or=75 years) with a diagnosis of first-time AMI between 1992 and 1997 and 13139 controls (matched to cases on age, sex, general practice attended, calendar time, years of prior history in the GPRD) were included. Overall, the relative risk estimate of AMI (adjusted for smoking, body mass index, hormone replacement therapy and aspirin) in current NSAID users was 1.17 (95% CI 0.99, 1.37). Long-term current NSAID use (>or=30 prescriptions) yielded an adjusted odds ratio (OR) of 1.20 (95% CI 0.94, 1.55). Stratification by age (<65 years vs>or=65 years) and sex did not materially change the results.

CONCLUSIONS

Our findings indicate that current NSAID exposure in patients free of diagnosed cardiovascular or metabolic conditions predisposing to cardiovascular diseases does not decrease the risk of AMI.

Obtaining evidence for use by healthcare payers on the success of chronic obstructive pulmonary disease management

Healthcare payers make decisions on funding for treatments for diseases, such as chronic obstructive pulmonary disease (COPD), on a population level, so require evidence of treatment success in appropriate populations, using usual routine care as the comparison for alternative management approaches. Such health outcomes evidence can be obtained from a number of sources. The 'gold standard' method for obtaining evidence of treatment success is usually taken as the randomized controlled prospective clinical trial. Yet the value of such studies in providing evidence for decision-makers can be questioned due to the restricted entry criteria limiting the ability to generalize to real life populations, narrow focus on individual parameters, use of placebo for comparison rather than usual therapy and unrealistic intense monitoring of patients. Evidence obtained from retrospective and observational studies can supplement that from randomized clinical trials, providing that care is taken to guard against bias and confounders. However, very large numbers of patients must be investigated if small differences between drugs and treatment approaches are to be detected. Administrative databases from healthcare systems provide an opportunity to obtain observational data on large numbers of patients. Such databases have shown that high healthcare costs in patients with COPD are associated with co-morbid conditions and current smoking status. Analysis of an administrative database has also shown that elderly patients with COPD who received inhaled corticosteroids within 90 days of discharge from hospital had 24% fewer repeat hospitalizations for COPD and were 29% less likely to die during the 1-year follow-up period. In conclusion, there are a number of sources of meaningful evidence of the health outcomes arising from different therapeutic approaches that should be of value to healthcare payers making decisions on resource allocation.

Clinical risk factors for venous thromboembolus in users of the combined oral contraceptive pill

AIMS

To estimate the risk of venous thromboembolism among women prescribed the oral contraceptive pill who have acute clinical conditions such as lower limb fractures, compared with women with idiopathic venous thromboembolism.

METHODS

A nested case-control analysis using the General Practice Research Database, January 1993 to December 1999 was carried out. The participants were women aged 15-39 years, prescribed third generation oral contraceptives (gestodene and desogestrel) or oral contraceptives containing levonorgestrel. The main outcome measures were odds ratios as a measure of the relative risk estimate for venous thromboembolism in women with clinical conditions that predispose to VTE.

RESULTS

The adjusted relative risk estimate for venous thromboembolism among patients with the acute clinical conditions, compared with those without such illness, and adjusted for oral contraceptive use, was 17 (95% CI 6.5, 46).

CONCLUSIONS

This paper documents the strong independent association between certain acute clinical conditions and venous thromboembolism in women prescribed oral contraceptives. Failure to accurately identify and exclude such patients from a study of the effect of oral contraceptives on the risk of venous thromboembolism would result in an underestimate of the risk of venous thromboembolism associated with oral contraceptives.

[The BIFAP project: database for pharmaco-epidemiological research in primary care]

OBJECTIVES

To create a data base (BIFAP) with information provided by primary care doctors from the National Health System who use a computer at work, to evaluate its validity as a source of pharmaco-epidemiological information and to use it for the study of the efficacy and safety of medicines.

JUSTIFICATION

Some data bases, such as the British GPRD, have shown great efficiency in pharmaco-epidemiological research and in analysis of alarm signals in pharmacovigilance: primary care doctors are in a very good position to obtain clinical information from their patients. It is recommended that the impact of medicines on various populations is evaluated, including of course those medicines most used in Spain.

PILOT PHASE

January 2000-end of 2003. 300-500 doctors took part: a) monitoring of certain recommendations on recording; b) dispatch every 2 or 3 months to the Spanish Medicines Agency (AEM) of anonymous information with its origin encrypted (basic demographic details, morbidity, prescriptions, other data of epidemiological relevance), which are analysed by computer to check whether they meet adequate recording standards; c) despatch to the AEM of copies of anonymous clinical reports from small samples of patients (for BIFAP validation studies).

FEASIBILITY AND PERSPECTIVES

If BIFAP were viable, a standardised procedure for its use and protocols to support it as a research tool would be put in place.

Evaluating the safety of medicines, with particular reference to contraception

Toxicological studies and clinical trials cannot be expected to predict all important adverse effects of medicines and contraceptives. Post-marketing surveillance is essentially an epidemiological task that involves detecting associations between drugs and events. The first alerts about drug safety problems have often come from case reports, but epidemiological studies are needed to confirm adverse (or beneficial) effects and to provide quantitative information. This article illustrates methodological principles by considering three examples from the field of contraceptive safety: oral contraceptives and breast cancer, intrauterine contraception and pelvic inflammatory disease, and newer oral contraceptives and venous thromboembolism. Key issues that emerge include bias and confounding, the place of subgroup analyses, random error, and the use of computerized databases. In research on contraceptive and drug safety, conclusions usually need to be based on careful assessment of multiple observational studies.

Association between aspirin and upper gastrointestinal complications: systematic review of epidemiologic studies

AIMS

Because of the widespread use of aspirin for prevention of cardiovascular diseases, side-effects associated with thromboprophylactic doses are of interest. This study summarizes the relative risk (RR) for serious upper gastrointestinal complications (UGIC) associated with aspirin exposure in general and with specific aspirin doses and formulations in particular.

METHODS

After a systematic review, 17 original epidemiologic studies published between 1990 and 2001 were selected according to predefined criteria. Heterogeneity of effects was explored. Pooled estimates were calculated according to different study characteristics and patterns of aspirin use.

RESULTS

The overall relative risk of UGIC associated with aspirin use was 2.2 (95% confidence interval (CI): 2.1, 2.4) for cohort studies and nested case-control studies and 3.1 (95% CI: 2.8, 3.3) for non-nested case-control studies. Original studies found a dose-response relationship between UGIC and aspirin, although the risk was still elevated for doses lower or up to 300 mg day(-1). The summary RR was 2.6 (95% CI: 2.3, 2.9) for plain, 5.3 (95% CI: 3.0, 9.2) for buffered, and 2.4 (95% CI: 1.9, 2.9) for enteric-coated aspirin formulations.

CONCLUSIONS

Aspirin was associated with UGIC even when used at low doses or in buffered or enteric-coated formulations. The latter findings may be partially explained by channeling of susceptible patients to these formulations.

Use of selective serotonin reuptake inhibitors and risk of developing first-time acute myocardial infarction

AIMS

Selective serotonin reuptake inhibitors (SSRIs) have been associated with serotonin depletion in platelets, potentially leading to abnormal aggregation and prolonged bleeding time. In view of the importance of serotonin in coronary thrombosis, and decreased platelet serotonin concentrations associated with SSRIs, the present study was performed to test the hypothesis of a decreased risk of acute myocardial infarction (AMI) associated with SSRIs.

METHODS

We conducted a population-based case-control analysis using the UK General Practice Research Database (GPRD). A total of 3319 patients aged 75 years or younger free of clinical conditions predisposing to ischaemic heart disease, with a first-time diagnosis of AMI between 1992 and 1997, and 13 139 controls without AMI matched to cases for age, sex, general practice attended, and calendar time were included. Conditional logistic regression was used to estimate relative risks.

RESULTS

Adjusted odds ratios (with 95% CI) for current use of SSRIs, non-SSRIs, or other antidepressants, compared to the group of nonusers of antidepressants were 0.9 (95% CI 0.5,1.8), 0.9 (95% CI 0.7,1.2), and 1.3 (95% CI 0.6,2.8), respectively. As compared with nonuse of SSRIs, current use (regardless of any other antidepressants used) resulted in an adjusted OR of 1.1 (95% CI 0.7,1.6).

CONCLUSIONS

The current analysis provides evidence that SSRI exposure does not substantially decrease the risk of developing first-time AMI in patients free of factors predisposing to ischaemic heart disease. However, due to relatively small numbers of exposed subjects and the resulting wide confidence intervals, further studies may be needed to document a lack of effect of SSRIs in subjects without pre-existing diseases predisposing to AMI.

Dimensions of alcohol-related social and health consequences in survey research

Dimensions of alcohol-related social and health consequences are approached from two different perspectives. First, classical approaches with factor analytic techniques are used to empirically determine the dimensionality of item batteries intended to measure harm. Second, a closer look is taken at theoretically underlying dimensions of social and health consequences and their association with alcohol consumption. Using as empirical material data from the US national survey of males aged 21-59 (N3) conducted in 1969, the following specific questions are discussed: (1) What are the underlying dimensions of alcohol-related social and health consequences? (2) How should the relation between alcohol consumption and consequences best be assessed (in terms of epidemiological traditions or social constructivist traditions)? (3) How can we best incorporate the time perspective into modeling the relationship between alcohol consumption and consequences? A first attempt is made to develop practical guidelines for future research on handling these problems.

Pharmacovigilance: a science or fielding emergencies?

Pharmacovigilance involves the assessment of risks and benefits of medicines. There are legal and regulatory aspects of this process, and the licensing of a new medicine is always provisional. The systems, in the past, have had limited statistical involvement, either in terms of personnel who are statistically trained, or in terms of statistical methods. This is changing. The high profile activities of pharmacovigilance have often been emergencies, though most is routine activity. Application of statistical thinking and of techniques is being done to help detect adverse effects of medicines rather earlier so that some emergencies may be avoided.

Statins and the risk of dementia

BACKGROUND

Dementia affects an estimated 10% of the population older than 65 years. Because vascular and lipid-related mechanisms are thought to have a role in the pathogenesis of Alzheimer's disease and vascular dementia, we did an epidemiological study of the potential effect of HMGCoA (3 hydroxy-3methylglutaryl-coenzyme A) reductase inhibitors (statins) and other lipid-lowering agents on dementia.

METHODS

We used a nested case-control design with information derived from 368 practices which contribute to the UK-based General Practice Research Database. The base study population included three groups of patients age 50 years and older: all individuals who had received lipid-lowering agents (LLAs); all individuals with a clinical diagnosis of untreated hyperlipidaemia; and a randomly selected group of other individuals. From this base population, all cases with a computer-recorded clinical diagnosis of dementia were identified. Each case was matched with up to four controls derived from the base population on age, sex, practice, and index date of case.

FINDINGS

The study encompassed 284 cases with dementia and 1080 controls. Among controls 13% had untreated hyperlipidaemia, 11% were prescribed statins, 7% other LLAs, and 69% had no hyperlipidaemia or LLA exposure. The relative risk estimates of dementia adjusted for age, sex, history of coronary-artery disease, hypertension, coronary-bypass surgery and cerebral ischaemia, smoking and body mass index for individuals with untreated hyperlipidaemia (odds ratio 0.72 [95% CI 0.45-1.14]), or treated with nonstatin LLAs (0.96 [0.47-1.97], was close to 1.0 and not significant compared with people who had no diagnosis of hyperlipidaemia or exposure to other lipid-lowering drugs. The adjusted relative risk for those prescribed statins was 0.29 (0.13-0.63; p=0.002).

INTERPRETATION

Individuals of 50 years and older who were prescribed statins had a substantially lowered risk of developing dementia, independent of the presence or absence of untreated hyperlipidaemia, or exposure to nonstatin LLAs. The available data do not distinguish between Alzheimer's disease and other forms of dementia.

Design issues for drug epidemiology

Despite the difficulties involved in designing drug epidemiology studies, these studies are invaluable for investigating the unexpected adverse effects of drugs. The aim of this paper is to discuss various aspects of study design, particularly those issues that are not easily found in either textbooks or review papers. We have also compared and contrasted drug epidemiology with the randomized controlled trial (RCT) wherever possible. Drug epidemiology is especially useful in the many situations where the RCT is not suitable, or even possible. The study base has to be defined before the appropriate cohort of subjects is assembled. If all of the cases are identified, then a referent sample of controls may be assembled by random sampling of the study base. If all of the cases cannot be assembled, a hypothetical secondary base may need to be created. Preferably, only new-users of the drug should be included, and the risk-ratio will be different for acute users and chronic users. Studies will usually only be possible when researching the unintended effects of drugs. It is difficult to study efficacy because of confounding by indication. In occasional circumstances it may be possible to study efficacy (examples are given). Discussion of the dangers of designing with generalisability in mind is provided. Additionally, the similarities in study design between drug epidemiology and the RCT are discussed in detail, as well as the design-characteristics that cannot be shared between the two methods.

Target drug programs and medication use evaluation

Target drug programs and medication use evaluations are activities that are undertaken to improve the correct use of drugs. These programs should focus on inappropriate drug use, drug use problems, optimizing use of drugs, and improving the level of patient care. To monitor the effects of the programs, several types of outcomes have been evaluated, such as economic and financial, clinical quality, quality of life, patient satisfaction, and collaborative practice. The methodology to classify and monitor drug use incorporates the classification system developed by the World Health Organization, which takes into account each drug's anatomic, therapeutic, and chemical classification. In order to avoid focusing only on drugs and drug costs in these programs, and to allow for monitoring the impact of the programs on clinical practice, linking drug data to patient data is stressed. Target drug programs improve the appropriate use of drugs, and by doing so, contribute to safe and rational use of drugs in society.

Reporting of adverse drug reactions by poison control centres in the US

BACKGROUND

Although US poison control centres manage approximately 30,000 adverse drug reactions each year, the extent of voluntary reporting of these events to the US Food and Drug Administration (FDA) MedWatch spontaneous surveillance programme is unknown.

METHODS

A survey was mailed to directors of all 72 US poison control centres during April 1999 to determine their practices and opinions on reporting adverse drug reactions. The survey requested information on the poison control centre staff's practices in reporting adverse drug reactions to the FDA MedWatch programme during 1998.

RESULTS

A total of 56 fully completed surveys were returned. Of the respondents, 30 had not directly submitted adverse drug reaction reports to the FDA, 22 had submitted 10 or less, and 4 had submitted a total of 47 during 1998. Reasons given for not routinely reporting adverse drug reactions included adverse drug reactions reporting is not part of the regular routine (20%), lack of time to complete forms (15%), inability to determine causality (13%), most reactions are already reported and not unique (10%), reporting to the FDA is too much work (9%), and responsibility rests with the attending physician (7%). Direct reporting to MedWatch of any cases of adverse drug reactions was more likely when the poison control centre was certified by the American Association of Poison Control Centers (p < 0.05; odds ratio = 5.1; 95% confidence interval 1.1 to 23.5); however, this practice was not associated with documenting deaths associated with adverse drug reactions, having more than 75% of the staff of the Poison Information Specialists composed of pharmacists or nurses, or managing greater than 20,000 or 34,000 human exposure cases during 1998. Approximately half of the poison control centres directly or indirectly reported some adverse drug reactions to the FDA by virtue of contacting the manufacturer or cooperating with postmarketing surveillance.

CONCLUSION

Poison control centres represent an underutilised source of reporting to MedWatch, but several internal and external obstacles limit the direct reporting of adverse drug reactions routinely.

Antibiotics in the prevention and treatment of coronary heart disease

Seroepidemiology, pathology, and animal studies provide evidence for a possible association between Chlamydia pneumoniae infections and atherosclerosis, coronary heart disease, and myocardial infarction. If this association exists, then exposure to certain antibiotics may positively affect the clinical course after an acute ischemic cardiac event (secondary prevention) and affect the risk of developing a first-time myocardial infarction (primary prevention). Preliminary evidence from clinical trials suggests that treatment with new macrolide antibiotics may improve outcome after ischemic events, and evidence from a large case-control analysis indicates that exposure to tetracyclines or quinolones may reduce the risk of developing a first-time myocardial infarction. However, antibiotics for the treatment or prevention of ischemic heart disease must not be recommended yet. This review of published studies briefly summarizes the currently available literature on the effects of antibiotics on the risk of developing coronary heart disease and myocardial infarction.

Evidentiary challenges to evidence-based medicine

The evidence-based medicine (EBM) movement has exerted a strong influence on contemporary medicine. It has been used to define the hierarchy of knowledge in clinical medicine by classifying clinical findings according to the perceived relevance and validity of the respective methodologies of studies from which evidence was collected. In the spectrum of theories of knowledge, EBM predominantly relies on findings obtained from population-derived clinical research. This reliance on knowledge obtained from population studies sharply contrasts with a physiologic model of clinical knowledge advocated by basic science researchers and many clinicians. An apparent schism between proponents of physiologic and population models in the approach to the practice of medicine has been created. This dichotomy between practising physicians and EBM physicians in the approach to clinical knowledge should not be irreconcilable. We advocate a consilient approach to the interpretation of evidence and the integration of medical knowledge. This approach relies on 'linking of facts and fact-based theory across various disciplines to create a common groundwork of explanation'.

Cardiovascular drug prescriptions and risk of depression in diabetic patients

Our aim was to investigate the association of calcium channel blocker (CCB), beta-blocker, and ACE inhibitor medications with the risk of depression in diabetic patients. A case-control study was performed using an automated database (MediPlus, IMS) of 400 primary care practices in Germany including 972 diabetic cases with newly diagnosed depression in 1996 (index date) and 972 diabetic controls, matched for age, sex, and index date. The odds ratios (95%-confidence intervals) for depression, adjusted for type of practice, number of visits and prescriptions, hospitalization, cardiovascular diagnoses, and renal failure, were 2.2 (95% CI: 1.2-4.2) for exposure to CCB 6 months prior to index date, 2.6 (95% CI: 1.1-7.0) for beta-blockers, and 1.3 (95% CI: 0.8-2.2) for ACE inhibitors, respectively. Adjusted odds ratio for CCB (4.3; 95% CI: 1.7-13.5) and beta-blockers (4.5; 95% CI: 1.2-29.5) were higher with daily dosages above the median. Prescriptions of CCB and beta-blockers among diabetic patients may increase the risk of depression. Because this association may alternatively be explained by cardiovascular comorbidity, further studies will be necessary to investigate the link between these cardiovascular medications and depression.